Tensioning apparatus for a lashing strap

Abstract

A tensioning apparatus for the step-wise tensioning and non-stepped releasing of a lashing strap includes a frame (1; 100), a pivot lever (2) having two pivot arms (16, 16'), and a ratchet mechanism that includes ratchet wheels (3, 3') and locking pawls (5, 5'; 105, 105'). By using a plurality of locking pawls (5, 5'; 105, 105'), the tensioning apparatus is able to absorb a greater lashing force or to tension the lashing strap in locking steps which differ from the tooth pitch t. To release the lashing strap, cams (40) on the pivot arms (16, 16') of the pivot lever (2) move the locking pawls and thus the ratchet mechanism to a disengaged position. The structural height of the tensioning apparatus and the number of components required for it may be reduced by using curved locking pawls (5, 5'; 105, 105'), a curved driving pawl (20), and a leg spring (41) which serves as the sole spring element for biasing the locking pawls.

What is claimed is: 
     
       1. A tensioning apparatus for a lashing strap having a fixed end and a free end, comprising: a frame having two side walls which extend parallel to one another, the fixed end of the lashing strap being operationally connected to the frame;   a wind-up spindle that is rotatably mounted on the frame and that receives the free end of the lashing strap; and   ratchet mechanism means for securing the wind-up spindle from rotation in a first direction with respect to the frame, the ratchet mechanism means including a ratchet wheel connected to the wind-up spindle,   first and second locking pawls that are mounted on the frame and moveable between an engaged position wherein the locking pawls contact the ratchet wheel and a disengaged position wherein the locking pawls are withdrawn from the ratchet wheel, the first locking pawl having a curved configuration so as to reduce the structural height required for the frame, and   biasing means for biasing the locking pawls toward the engaged position,     wherein the first locking pawl is shaped as a ring segment,   wherein each side wall of the frame has a respective first pawl guide slot through which the first locking pawl extends, the first pawl guide slots conforming to the curved configuration of the first locking pawl and being shaped as ring segments, and   wherein each side wall of the frame additionally has a second pawl guide slot through which the second locking pawl extends.   
     
     
       2. The tensioning apparatus of claim 1, wherein the side walls of the frame extend in a longitudinal direction, and wherein a cross section of the frame taken in a transverse direction that is perpendicular to the transverse direction is generally U-shaped, with the side walls providing the legs of the U. 
     
     
       3. The tensioning apparatus of claim 2, wherein the pawl guide slots extend generally in the longitudinal direction and have inner ends that are oriented toward the ratchet wheel and outer ends that are oriented away from the ratchet wheel, the inner ends of the pawl guide slots in a side wall being closer than the outer ends of the pawl guide slots in the same side wall, and wherein the tensioning apparatus further comprises means for securing the locking pawls from displacement in the transverse direction. 
     
     
       4. The tensioning apparatus of claim 1, wherein the first locking pawl has a concave side and a convex side, wherein the second locking pawl also has a curved configuration, with a concave side and a convex side, wherein the second pawl guide slot is curved, and wherein the first and second pawl guide slots are disposed in such a manner that the concave sides of the locking pawls face one another. 
     
     
       5. The tensioning apparatus of claim 4, wherein the second locking pawl is also shaped as a ring segment, wherein the second pawl guide slots are also shaped as ring segments, wherein the locking pawls have forward ends that are directed toward the ratchet wheel, wherein the pawl guide slots guide the locking pawls for sliding moving toward or away from the ratchet wheel, and wherein the front ends of the locking pawls move toward each other as the locking pawls slide toward the ratchet wheel. 
     
     
       6. The tensioning apparatus of claim 4, wherein the biasing means comprises a leg spring having a coiled portion and first and second legs that extend from the coiled portion, the first leg of the leg spring contacting the first locking pawl, the second leg of the leg spring contacting the second locking pawl, and the coiled portion of the leg spring being mounted between the concave sides of the locking pawls. 
     
     
       7. The tensioning apparatus of claim 1, wherein the ratchet wheel has a plurality of teeth, each having a leading edge and a trailing edge, and wherein the locking pawls are positioned so that, when they are in their engaged position, one locking pawl touches the leading edge of a tooth and the other locking pawl touches the trailing edge of another tooth. 
     
     
       8. The tensioning apparatus of claim 7, wherein the locking pawls have forward ends that are directed toward the ratchet wheel, wherein the ratchet wheel has a predetermined tooth pitch, and wherein the forward ends of the locking pawls are separated by a distance corresponding to one and a half times the tooth pitch when the locking pawls are in their engaged position. 
     
     
       9. The tensioning apparatus of claim 1, wherein the biasing means comprises a first spring which urges the first locking pawl toward the ratchet wheel and a second spring which urges the second locking pawl toward the ratchet wheel. 
     
     
       10. The tensioning apparatus of claim 1, wherein the biasing means comprises a common spring element which urges both locking pawls toward the ratchet wheel. 
     
     
       11. The tensioning apparatus of claim 10, wherein the locking pawls have forward ends that are directed toward the ratchet wheel and rear ends that are directed away from the ratchet wheel, and wherein the common spring element comprises a leg spring having first and second oppositely disposed legs, the first leg lying against the rear end of the first locking pawl and the second leg lying against the rear end of the second locking pawl. 
     
     
       12. The tensioning apparatus of claim 10, wherein the frame further comprises a holding bar which projects toward the ratchet wheel, the common spring element being mounted on the holding bar. 
     
     
       13. The tensioning apparatus of claim 1, further comprising: a pivot lever having a bearing end, the wind-up spindle extending through the bearing end to mount the pivot lever for pivoting movement with respect to the frame, the pivot lever being pivotal in the first direction and in a second direction that is opposite the first direction; and   driving means, carried by the pivot lever and cooperating with the ratchet wheel, for rotating the wind-up spindle in the second direction when the pivot lever is manually pivoted in the second direction.   
     
     
       14. The tensioning apparatus of claim 13, wherein the driving means comprises a driving pawl that is movably mounted on the pivot lever. 
     
     
       15. The tensioning apparatus of claim 14, wherein the ratchet wheel has teeth, the biasing means urging the locking pawls toward the teeth of the ratchet wheel, and wherein the driving means further comprises means for biasing the driving pawl toward the teeth of the ratchet wheel. 
     
     
       16. The tensioning apparatus of claim 14, wherein the driving pawl is curved and has a concave side, the concave side of the driving pawl facing the frame. 
     
     
       17. The tensioning apparatus of claim 1, wherein the first pawl guide slots have a constant width, wherein the second pawl guide slots have a constant width, and wherein the width of the first pawl guide slots is the same as the width of the second pawl guide slots.